Author Topic: Basic Rocket Science Q & A  (Read 502256 times)

Offline Wolfram66

Re: Basic Rocket Science Q & A
« Reply #1140 on: 04/03/2019 01:39 am »
This will give you an idea of the weirdness that goes on at triple point of CycloHexane



Offline IanO

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Re: Basic Rocket Science Q & A
« Reply #1141 on: 04/11/2019 03:38 pm »
Why is wind shear a problem for modern launches?  Were there historical launch failures due to wind shear?  Are there different rocket designs which allow launching through wind shear and what are the tradeoffs?
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Offline mme

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Re: Basic Rocket Science Q & A
« Reply #1142 on: 04/11/2019 05:58 pm »
Why is wind shear a problem for modern launches?  Were there historical launch failures due to wind shear?  Are there different rocket designs which allow launching through wind shear and what are the tradeoffs?
I don't have specific numbers but ... Wind shear causes a sudden sideways moment on the rocket, starting at the nose and then proceeding down the vehicle. Both payloads and the rocket itself are much stronger in the vertical axis than they are to lateral forces. Part of the agreement when launching is that both the lateral and axial g-loads will be constrained within known limits and exceeding those constraints could damage the payload itself and lead to mission failure.

And the F9 is really long and skinny which may make it more sensitive to flexing and developing harmonic oscillations. But now I'm mostly hand waving...
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Offline intelati

Re: Basic Rocket Science Q & A
« Reply #1143 on: 04/11/2019 08:38 pm »
Were there historical launch failures due to wind shear?

Not exactly sure how to ascribe the failure of Challenger between the booster O-Rings, Joint design, and the wind shear, but Challenger hit unprecedented wind shear before the break up of the vehicle

e:Columbia Challenger
« Last Edit: 04/12/2019 08:05 pm by intelati »
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Offline sunworshipper

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Re: Basic Rocket Science Q & A
« Reply #1144 on: 04/11/2019 08:48 pm »
Were there historical launch failures due to wind shear?

Not exactly sure how to ascribe the failure of Columbia between the booster O-Rings, Joint design, and the wind shear, but Columbia hit unprecedented wind shear before the break up of the vehicle
Do you mean Challenger?

Offline cebri

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Re: Basic Rocket Science Q & A
« Reply #1145 on: 04/23/2019 02:41 pm »
Yes, wind shear was the last nail in the coffin for Challenger. The o-ring had already failed, but both the melted o-rings and the fuel from the SRM had solidified at launch and had created a very fragile seal.  The seal it is believed to have been broken when Challenger encounter unusual strong high winds, the SRB tried to compensate to keep Challenger on course, which put a lot of pressure on the seal until it finally broke. It is hard to say whether Challenger could have survived if it hand't encountered those winds, as the shuttle was also going through max-q when the seal broke off.
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Offline Jim

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Re: Basic Rocket Science Q & A
« Reply #1146 on: 04/23/2019 06:37 pm »
Why is wind shear a problem for modern launches?  Were there historical launch failures due to wind shear?  Are there different rocket designs which allow launching through wind shear and what are the tradeoffs?

Always been a problem.  Longer vehicles are more susceptible to them.
Day of launch I-loads is what is used to deal with them.  Not so much the vehicle design themselves.

But generally a more squat or stiffer vehicle is less affected by shear.

Offline Bananas_on_Mars

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Re: Basic Rocket Science Q & A
« Reply #1147 on: 05/18/2019 09:02 pm »
I've been wondering wether some of the proposed lunar landers (for example Blue Moon) could do part of TLI and possibly LOI with their landing engine and the use of some kind of "drop tanks"?

Is there any launch system that used or uses some kind of "drop tank" (besides Shuttle external tank)?

My reasoning is that once the lander would be in orbit, you don't have to worry about gravity losses any more, so a small engine would be enough for TLI. And such a drop tank should have much lower dry weight than a second stage, could be a simple stainless steel balloon tank. And since it's dropped before landing, it doesn't need to withstand the landing when empty.

Of course this adds complexity, i understand that. It might make some kind of Apollo style transposition and docking maneuver necessary. What else am I overlooking?

Offline A_M_Swallow

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Re: Basic Rocket Science Q & A
« Reply #1148 on: 05/19/2019 04:02 pm »
I've been wondering wether some of the proposed lunar landers (for example Blue Moon) could do part of TLI and possibly LOI with their landing engine and the use of some kind of "drop tanks"?

Is there any launch system that used or uses some kind of "drop tank" (besides Shuttle external tank)?

My reasoning is that once the lander would be in orbit, you don't have to worry about gravity losses any more, so a small engine would be enough for TLI. And such a drop tank should have much lower dry weight than a second stage, could be a simple stainless steel balloon tank. And since it's dropped before landing, it doesn't need to withstand the landing when empty.

Of course this adds complexity, i understand that. It might make some kind of Apollo style transposition and docking maneuver necessary. What else am I overlooking?


Refuelling the lander at a propellant depot or from a propellant tanker is the practical equivalent of using drop tanks.

Offline turbopumpfeedback2

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Re: Basic Rocket Science Q & A
« Reply #1149 on: 07/22/2021 09:54 pm »
The thrust vector control hobby rockets are very popular right now. It takes a lot of time, knowledge and other stuff to make one.

So I am completely shocked to see a liquid nitrogen rocket without fins and with no tvc fly perfectly straight during the boost phase, after flipping the bottle with liquids, e.g. this video at 7:26:



Why? Why does it not tumble?

It gains at least couple of meters per second (probably about few tens of meters per second) and much much smaller angular velocity. The center of mass due to sloshing should be way off.

« Last Edit: 07/22/2021 09:59 pm by turbopumpfeedback2 »

 

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